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pH shot up (and so did TA) way more than anticipated

FC: 4/5
pH: 7.8
TA 120

Last night, our pH was 7.2, with TA at about 80. I used the pool calculator and calculated that I needed 32 ounces of soda ash to increase ph to 7.5 and TA by about 9.1.

This morning, I just checked it and our pH is 7.8 and TA 120. I know this seems to still be within parameters, but I am wondering why it went up so much. Don't really want either of them going up anymore, however. We haven't swam, aerated or anything to make the pH climb so much. Last time when I added soda ash at the same numbers, using the calculator, it worked like a charm. (It's always a possibility I calculated the TA incorrectly this time around I guess.)

The pool water looks clear. Just wondering if I should do anything at this point, or leave it be and see where it takes us.

Re: pH shot up (and so did TA) way more than anticipated

There is no rush to adjust anything at the moment as the pH and TA are in range although at the upper limit. Make sure the water has been circulated for an hour and test again to see if they repeat.

Does the pH normally drop for you? If so, leave it alone and keep track of it every day to see what happens. If not, then you might want to lower the pH to 7.5 and see how long it takes to rise again. If the pH wants to climb faster than normal, lower it to 7.2 each time and that will drive the TA lower if your fill water is not too high in TA.

Re: pH shot up (and so did TA) way more than anticipated

There is no rush to adjust anything at the moment as the pH and TA are in range although at the upper limit. Make sure the water has been circulated for an hour and test again to see if they repeat.

Does the pH normally drop for you? If so, leave it alone and keep track of it every day to see what happens. If not, then you might want to lower the pH to 7.5 and see how long it takes to rise again. If the pH wants to climb faster than normal, lower it to 7.2 each time and that will drive the TA lower if your fill water is not too high in TA.

You know, I just realized I tested when the water was only circulating for about 30-45 minutes. I probably should have waited longer. You're right. I will retest a little later to see what I get.

Our pH actually has a tendency to drop it seems. Not sure if it's from the recent waves of rain we have had, not enough sun lately, or what, but so far that seems to be the trend. I will leave it be for now and see where it goes from here We are getting lots of sun today though.

Is there a time period you should wait between introduction of soda ash for raising the pH and muriatic/dry acid to lower it if it gets too high? Hypothetical: Say I added soda ash last night and our pH shot threw the roof where it became too high and I needed to counteract that...Could I add muriatic acid shortly thereafter to lower the pH? It can't only be a half an hour is it?

Also, what do you mean by "fill water" here: "that will drive the TA lower if your fill water is not too high in TA."

Re: pH shot up (and so did TA) way more than anticipated

I would let the pool run for a good hour before adjusting with acid. It wont hurt to run for only an hour and you want to make sure that you don't compound one error with another. If you made a major mistake with the soda ash, then that is another subject not to be confused with slightly out of range recommendations.

The fill water is the water that you use to fill the pool when it gets too low from evaporation, splash out, etc. If the fill water is high in TA, then the fill water will tend to raise the TA in the pool when the water is added. Since your TA was 80 ppm, I suspect that the fill water is not high in TA, and with time, acid additions will lower the TA on its own.

Watch the pH closely for now, and if it rises above 7.8 use some acid to lower it to 7.5.

Re: pH shot up (and so did TA) way more than anticipated

Originally Posted by ping

I would let the pool run for a good hour before adjusting with acid. It wont hurt to run for only an hour and you want to make sure that you don't compound one error with another. If you made a major mistake with the soda ash, then that is another subject not to be confused with slightly out of range recommendations.

The fill water is the water that you use to fill the pool when it gets too low from evaporation, splash out, etc. If the fill water is high in TA, then the fill water will tend to raise the TA in the pool when the water is added. Since your TA was 80 ppm, I suspect that the fill water is not high in TA, and with time, acid additions will lower the TA on its own.

Watch the pH closely for now, and if it rises above 7.8 use some acid to lower it to 7.5.

Thank you Just got some dry acid (pH Down) from Home Depot just in case but hoping I don't have to use it.

Re: pH shot up (and so did TA) way more than anticipated

Either way I wouldn't worry about your TA for now. When/if your ph goes up to 7.8, lower it back down to 7.2 with MA or ph down and your TA will end up finding it's "happy place".

Oh, I totally preferred muriatic acid. However, after reading in Pool School how dangerous muriatic acid can be if handled improperly, and how dry acid is easier to handle, I got nervous and didn't want my husband messing with MA if there was an alternative

Do you mean when my pH goes higher than 7.8? It's been at/about 7.8 (or could be 7.7, always hard to tell) consistently since this morning. I just retested and it didn't budge. I was going to just let it go for a bit and make sure it doesn't increase higher than 7.8, and if so, I was going to add the pH Down.

Re: pH shot up (and so did TA) way more than anticipated

There can be a problem with sulfate buildup from using very large amounts of dry acid. If sulfate levels get high enough they can damage the coating on the SWG cell plates and potentially cause plaster problems as well. This is normally only an issue if you are using dry acid constantly, as low levels have no real impact.

So it seems since you have a vinyl liner and no swg, there may be no real risk, but it still goes somewhat against only adding to your pool what your pool needs.

So, in my opinion, if you only occasionally have to use dry acid I doubt it is a problem, but if lowering ph becomes a constant event, then I would switch to MA to avoid potential issues. Care needs to be taken in handling MA, but most of us on here use it as our preferred ph lowering solution.